Until recently, there were only two basic types of multi-shed weaving systems. These systems are (1) flat weft-wave systems, i.e., those in which a multiplicity of sheds move in the weft direction along a flat path, and (2) curved warp-wave or rotor systems, i.e., those in which a multiplicity of sheds move in the warp direction along a curved path. These weaving systems suffer from several disadvantages, one of the most critical disadvantages being the severe limitation in the diversification of weaves available due to the inability to use standard shed-forming mechanisms.
In the applicant's U.S. Pat. No. 4,122,871, there is disclosed a third type of multi-shed weaving which overcomes many of the disadvantages of the flat weft-wave systems and the curved warp-wave systems. This new and improved multi-shed weaving technique involves the use of flat warp-wave systems, i.e., those in which a multiplicity of sheds move in the warp direction along a flat path.
Along with the development of curved warp-wave weaving systems, the prior art has also developed apparatus for inserting weft threads into a plurality of warp sheds as they move in a direction parallel to the warp threads. For example, such prior art systems are disclosed in Gentilini U.S. Pat. No. 2,742,058, and British Pat. No. 819,974. However, all of these prior art systems, and those similar to them, utilize needles, rapiers, or like members, of either the flexible or rigid type, which members remain attached or connected to the weaving machine during their traversal through the moving warp sheds to lay the weft thread. Therefore, it is necessary in such systems to retract the weft-laying member to the side of the machine from which the weft thread is supplied. Such an arrangement has the disadvantage of using one-half of the time interval that the weft-laying member is within the warp shed for the non-productive motion of withdrawal or retraction of the weft-laying member from the shed after laying of the weft thread.
This drawback was recognized in the applicant's U.S. Pat. No. 4,122,871, which discloses method and apparatus for employing shuttles for simultaneously laying weft threads in a plurality of moving warp sheds. More particularly, U.S. Pat. No. 4,122,871 discloses the use of shuttles for simultaneously laying more than one weft thread in a warp-wave weaving system, wherein the shuttles are fired from at least one side of the machine, through the moving warp sheds, and are stopped on the other side of the machine. The shuttles are unconnected to the machine during their traversal of the moving warp sheds, and it is therefore unnecessary to retract the shuttles through the moving sheds. In this manner, the shuttles operate to lay weft threads in the moving sheds of a warp-wave weaving system during the entire time that the shuttles traverse the moving sheds.
In the applicant's U.S. Pat. No. 4,122,872 there is disclosed an improved weft-laying system for warp-wave weaving systems, wherein the weft threads are accurately and continuously guided to move in a lateral direction in unison with the laterally moving warp sheds during the transversal of gripper shuttles through the warp sheds. More particularly, the gripper shuttles are fired into moving warpsheds which move in a direction perpendicular to the direction in which the gripper shuttles are initially fired.
Single-phase weaving systems have been developed wherein weft threads are inserted into an open shed by a fluid jet, such as a jet of water or air, which in the case of air is directed through a weft-guiding channel removably positioned within the open shed (see, for example, U.S. Pat. Nos. 3,818,952; 3,821,972; 3,847,187; 4,116,243 and 4,125,133). The weft-guiding channel is necessary so as to partially confine the jet of fluid within the open shed, thereby maintaining the speed of the jet at a velocity required for picking the weft thread while inhibiting the jet from interfering with warp threads forming the open shed.
There are several advantages and benefits derived from the use of fluid jets in connection with the insertion of weft threads. For instance, fluid jets result in faster weft insertion. Also, fluid jets are relatively easy and inexpensive to manufacture and maintain. However, these improvements have been realized at the cost of additional energy requirements resulting from the large amount of air required due to the partial confinement of the air jet within the weft-guiding channel. Also, the partially open weft-guiding channels create the possibility that the weft thread may inadvertently escape from the weft-guiding channels, resulting in a reduction in quality and productivity.
Attempts have been made to provide substantially closed weft-guiding channels (see, for instance, U.S. Pat. No. 3,828,828 and U.S. Pat. No. 3,796,236). These attempts suffer, however, from the disadvantage of requiring additional time to close the channel, thereby decreasing the time available for weft insertion. Because of this reduced time for weft insertion, additional energy is required to successfully insert the weft thread in the shorter time available for weft insertion, thereby offsetting the energy savings gained by the use of the substantially closed weft-guiding channels. To date, no one has taught how fluid jets could be employed in a multi-phase weaving system.